Tube Heat Exchanger Research Articles

Enhancing of low-temperature deformation compatibility of pure titanium welded tube by laser welding and cold-worked in welded zone

This study is aimed to improve the low-temperature deformation behaviour of titanium heat exchange tubes by optimizing welding method and weld treatment processes. The various welding processes and cold-worked in welded zone process are adopted, and the effects of macro-morphology, microstructure and mechanical properties on low-temperature deformation behaviour are studied. The results show that the width of the laser welded joint and welded zone is 3.8 mm and 2.9 mm respectively, which is 40% and 63% of TIG welded joint. Especially, the width of heat affected zone and the grain size of laser welded joint are obviously reduced due to its concentrated energy density. The cold-worked process in welded zone can relieve the macroscopical and microstructural discontinuity between base metal, heat affected zone and welded zone. The inner weld reinforcement is eliminated to improve smooth transition and the columnar α grains in welded zone are remarkable fragmented with plenty of twins. The hardness of the welded zone after cold-worked is significantly higher than that of the base metal, resulting in base metal being the main deformation area of the welded tube at low temperature, which is beneficial to improve the deformation performance of the whole welded tube. By adapting the cold-worked and laser welding process with smooth transition and narrower weld width, the pure titanium welded tube can meet the requirement of three times low-temperature deformations.

Comparative study of heat exchanger tubes failure analysis using ECT and IRIS

Comparative study of heat exchanger tubes failure analysis using ECT and IRIS

Simulation study of heat transfer behaviour of turbulent two-phase flow in a 3D cubic shell and tube heat exchanger using water and different nanofluids

This research utilizes a two-phase flow model to replicate the thermal exchange in a counter flow shell and tube heat exchanger, comparing the efficacy of different nanofluids against pure water. The shell space is represented as a closed cubic area filled with diverse fluids, while the tube functions as the thermal exchange component. It investigates parameters like nanofluid variations, nanoparticle dimensions, and volume ratios to enhance the efficiency of temperature exchange between the shell and tube fluids. The Reynolds-averaged Navier-Stokes (RANS) technique is employed to analyze turbulence within the heat exchanger, utilizing ANSYS@FLUENT (Version 2022 R1) for simulations, which were considered reliable when convergence criteria reached 10−5. The outcomes are assessed based on velocity, thermal conductivity, Nusselt number, temperature dispersion, and turbulent kinetic energy. Notably, the results underscore that integrating nanoparticles into the fluid amplifies its thermal conductivity, with higher concentrations yielding more significant enhancements. Nanofluids, particularly those comprising SiO2-H2O with small nanoparticles and high volume fractions, exhibit notable improvements in heat transfer compared to pure water. TiO2-H2O follows in second place, trailed by CuO-H2O and Al2O3-H2O. The application of the RANS method effectively elucidates turbulence patterns and their impact on heat transfer dynamics between the shell and tube. An increase in Reynolds number has shown an adverse effect on heat transfer. Overall, this study furnishes valuable insights for optimizing heat transfer performance in such systems.

Numerical Investigation of Shell-Nozzle Diameter Effect on Thermal Performance of Shell-and-Tube Heat-Exchanger

The shell nozzle diameter plays a crucial role in determining heat transfer efficiency and pressure characteristics in shell and tube heat exchangers. In this study, we have conducted a numerical simulation to explore the effects of varying shell nozzle diameters on heat transfer performance, flow behavior, and pressure drop within a shell and tube heat exchanger. Ranging from 10 to 110 mm, we assessed how altering the shell nozzle diameter affected heat transfer, flow patterns, and pressure drop. Employing the k-ω shear stress transport turbulence model, we compared numerical Nusselt numbers to experimental data, observing a correlation. As the shell nozzle diameter decreased, inlet velocity surged, generating a stronger vortex. Shrinking from 110 to 10 mm, this reduction amplified vorticity by an average of 169%, notably intensifying heat exchange by 35%. Evaluating the overall heat transfer coefficient against pressure drop, we used the thermal enhancement factor, reaching a peak of 4.39 at a 70 mm shell nozzle diameter. This exploration lays groundwork for optimizing shell nozzle diameters in these heat exchangers.

Numerical investigation and software design for internally finned helically coiled tubes heat exchangers with single-stream and multi-stream

To enhance the heat transfer inside the helically coiled tubes, a kind of internally finned helically coiled tubes is proposed. Compared to the smooth helically coiled tubes, the heat transfer and flow resistance characteristics of internally finned helically coiled tubes are investigated numerically. Influence of fin number, pitch and coil diameter on the performance is analyzed. Empirical correlations to calculate the Nusselt number and friction factor of internally finned helically coiled tubes are summarized. The helically coiled tubes heat exchangers are divided equally into several cells and the theoretical analysis of energy flow in each cell is carried out. According to the established equations of heat transfer, the calculation method for single-stream helically coiled tubes heat exchangers and multi-stream helically coiled tubes heat exchangers is proposed. The geometric model and thermohydraulic model are built up, and the design software for internally finned helically coiled tubes heat exchangers is developed based on Python. Take two cases of helically coiled tubes heat exchangers as examples, smooth helically coiled tubes and internally finned helically coiled tubes (fin number is six) are applied to validate the accuracy of calculations results obtained by design software. The results show that the deviation of outlet temperature and pressure drop is less than 7 % and 11 %, respectively. When applying internally finned helically coiled tubes, the heat transfer coefficient of the tube side is increased by approximately 30 %. The corresponding pressure drop and heat load is higher. The outlet temperature proves that the heat transfer is more insufficient in the case of internally finned helically coiled tubes (fin number is six).

Improvement in heat transfer and flow pattern of sprayed falling on horizontal tubes with rib structure for a sewage source heat pump

The falling film flow and heat transfer characteristics are critical to improve the performance of spray heat exchangers in a sewage source heat pump (SSHP), which is influenced by the operating and structural parameters. Therefore, considering the unique flow patterns of wastewater falling film caused by the oily content, and the influence of heat exchange tubes with surface structures on flow and heat transfer, two types of heat exchanger tubes with axial and circumferential ribs were designed and the falling flow over tubes were investigated through CFD method using VOF model. The falling film flow pattern, liquid film coverage and heat transfer coefficient (HTC) outside the ribbed heat exchange tubes were investigated, and the influence of rib structures and Re were analyzed. It was found that oily wastewater liquid film spreaded differently depending on the rib structures, and circumferential ribs of case 2 improved the flow pattern by increasing film coverage, which obviously affected the tube HTC. At higher Re, the ribbed tubes displayed higher potential in better heat transfer performance. Therein, the circumferential ribbed tubes showed highest average HTC, with up to 31.9 % higher than smooth tubes, which can be further enhanced by increasing Re. This study provides a foundation for enhancing the heat transfer performance of spray heat exchangers in sewage source heat pumps through the design and modification of tube surface structures.

Nonlinear FOPID controller design for pressure regulation of steam condenser via improved metaheuristic algorithm

Shell and tube heat exchangers are pivotal for efficient heat transfer in various industrial processes. Effective control of these structures is essential for optimizing energy usage and ensuring industrial system reliability. In this regard, this study focuses on adopting a fractional-order proportional-integral-derivative (FOPID) controller for efficient control of shell and tube heat exchanger. The novelty of this work lies in the utilization of an enhanced version of cooperation search algorithm (CSA) for FOPID controller tuning, offering a novel approach to optimization. The enhanced optimizer (en-CSA) integrates a control randomization operator, linear transfer function, and adaptive p-best mutation integrated with original CSA. Through rigorous testing on CEC2020 benchmark functions, en-CSA demonstrates robust performance, surpassing other optimization algorithms. Specifically, en-CSA achieves an average convergence rate improvement of 23% and an enhancement in solution accuracy by 17% compared to standard CSAs. Subsequently, en-CSA is applied to optimize the FOPID controller for steam condenser pressure regulation, a crucial aspect of heat exchanger operation. Nonlinear comparative analysis with contemporary optimization algorithms confirms en-CSA’s superiority, achieving up to 11% faster settling time and up to 55% reduced overshooting. Additionally, en-CSA improves the steady-state error by 8% and enhances the overall stability margin by 12%.

Numerical simulation and multi-objective optimization design of conjugate heat transfer in novel double shell-passes multi-layer helically coiled tubes heat exchangers

A novel double shell-passes multi-layer helically coiled tubes heat exchanger (DSMHCTHE) is proposed to improve the flow and heat transfer performance of the shell side. It was studied by using conjugate heat transfer numerical model. By changing coil diameter and pitch, the influence of coil torsion on the performance of the heat exchangers was investigated in the range of 0.0637–0.3183, and compared with the conventional multi-layer helically coiled tubes heat exchangers (MHCTHE). Two kinds of heat exchangers were optimized by using multi-objective optimization differential evolution algorithm. The results indicate that the coil pitch has a greater effect on the overall heat transfer coefficient, and the effects of coil pitch variations in the inner and outer helically coiled tubes follow different patterns. Compared with MHCTHE, the heat transfer rate of DSMHCTHE are increased by 13.9 %–19.1 %, the comprehensive performance is increased by 13.0 %–18.0 %, and the heat transfer entropy generation number and friction entropy generation number are lower. It shows that DSMHCTHE have better application potential as heat exchangers.

Thermal effectiveness analysis of heat exchange tube with staggered louver-punched V-baffles

An experiment has been conducted to ascertain the optimal approach for enhancing the convective transmission of heat in a heat exchanger tube by periodically positioning staggered louver-punched V-baffle (SLVB) vortex generators on a perforated tape. The louver-punched V-baffles were staggered and set up with two patterns: V-apex directing upstream (VU) and downstream (VD), and each featured a louver-punched aperture to minimize friction loss. The aim of this work was to rise the thermal effectiveness as well as the Nusselt number ratio (NuR) at optimal effectiveness in order to cut down on overall dimension of heat exchangers. Consequently, the research findings focused on behaviors of heat transmission and frictional loss, incorporating generated entropy, through a variety of Reynolds numbers (Re) spanning 29,270 to 4762. The SLVB elements were designed and placed in VU and VD forms using three relative pitches (PR = 0.5, 1.0, and 1.5) as well as six louver-flapped angles (θ = 0°, 10°, 20°, 30°, 45°, and 90°), all at the same attack angle (α = 52°), a baffle height ratio (BR = 0.3) and a louver size ratio (LR = 0.73). As demonstrated by the experiment, the θ = 20° generated the best heat transfer of all PR values, up to 6.55 times greater than the smooth tube, despite having a lower friction loss than the θ = 0° (solid baffle). At PR = 0.5, θ = 20° and smaller Re, the optimum thermal effectiveness factor (TEF) and NuR values were, respectively, about 2.65 and 6.55 for the VU SLVB and 2.52 and 6.04 for the VD one. It implied that the TEF strategies can be utilized to anticipate the best effectiveness under identical scenarios. Also, correlations for the critical parameters, namely, Nu, f, and TEF, were estimated and documented.

THE DYNAMICAL INVESTIGATION OF HEAT TRANSFER AND TEMPERATURE CHANGES OF THE SHELL AND TUBE HEAT EXCHANGER USING THE LYAPUNOV METHODS

The dynamic of the heat transfer analysis constitutes an important factor that has drawn the attention of many researchers. Heat transfer is evaluated by considering the heat transfer coefficient, the surface area, and the temperature difference between the surface and the surrounding fluid. The computation of the temperature difference across various surface areas shows that increased heat transfer enhances the proportion of the heat conduction rate. In most cases, the system becomes unstable because inappropriate structural elements and outside disturbances, like ambient temperature can readily change the yielding temperature. As a result, the heat exchanger's efficiency needs improvement. A numerical simulation analyzing the performance of a shell and tube heat exchanger indicates that an increase in the surface area leads to a corresponding increase in the heat transfer rate. To optimize system performance, mathematical models were employed for the stability analysis of temperature changes. MATLAB simulations computed temperature differences in quantities of heat and area, thereby obtaining valuable insights for improving heat exchanger design and operation.

Self-excited oscillation characteristics and mechanisms of supercritical CO2 flowing in a Helmholtz oscillator for enhancing heat transfer

The drastic variations in thermal properties of supercritical CO2 near its pseudo-critical point induce the formation of complex boundary layer structures within pipelines, rendering it susceptible to heat transfer deterioration under the influence of buoyancy forces. The Helmholtz self-excited cavity can generate self-excited pulsating jets, enhancing the intermixing between fluids inside the heat exchanger tubes, disrupting the thermal boundary layer, and suppressing heat transfer deterioration. In this study, the characteristics and mechanisms of self-excited oscillations of supercritical CO2 flowing vertically upward in the Helmholtz self-excited cavity were investigated using the large eddy simulation (LES) method. A detailed analysis of cavitation and vortex evolution within the cavity was conducted, along with an exploration of the influence of inlet pressure and structural parameters on the frequency characteristics of pulsations. The results indicate a close relationship between cavitation and vortex interactions and the pulsation frequency. An increase in inlet pressure leads to a significant cavitation phenomenon near the jet shear layer and an increase in vortex frequency. Dimensionless cavity length (Lc/d1) enlargement results in an increase in outlet pulsation frequency but a decrease in pulsation amplitude. The critical dimensionless ratio of cavity diameter (Dc/d1) plays a crucial role in maintaining the desired pulsation frequency and amplitude. Within the working range outlined in this paper, practical insights for system design and operation are provided by the optimal parameters of Lc/d1 = 3 and Dc/d1 = 10.

Review and Thermal Calculation of a Shell and Tube Heat Exchanger with Baffles in Cross - Counter Flow Arrangement

In one pass shell and tube heat exchanger with baffles one fluid flows inside of parallel tubes and other fluid flows outside of tubes in perpendicular to tube axis changing alternately its direction. Passing the window of the baffles the shell side fluid deviates its flow direction rapidly. This creates just behind the window of each baffle a so-called “dead volume” which renders a stagnation of flow. This dead volume assumed to be triangular in shape causing the flow behind the window to be conical.In this thermal model the “dead volume” taken into account and change of temperature of the shell side fluid during its flow from tube to tube is considered. The thermal analysis of the cross- counter flow arrangement for any number of tube in bundle with progressive changes in tube length has been carried out. The numerical computations with different tube and baffle numbers are performed. It is found that at the beginning the effectiveness of the heat exchanger increases distinctly with increasing tube number and baffle number. But after certain number of tube and baffles the increasing rate weakens and it becomes very small. Due to the presence of “dead volume” there is reduction in the thermally active heat transfer surface area which leads to a smaller value of Number of Transfer Units (NTU). Hence, the results of computation obtained in this paper with the consideration of the “dead volume” will provide lower value of the effectiveness than that of without the consideration of it.

Enhancing heat transfer performance in forced convective systems using experimental study with crystalline nano cellulose-dispersed H2O/C2H6O2 nanofluids

This work examines the heat transfer properties of a forced convection circular tube heat exchange system employing a nanofluid made of crystalline nano cellulose (CNC) diluted in a 60:40 ratio of distilled water (H2O) and ethylene glycol (C2H6O2). The objective is to measure the generated nano-fluid's thermal characteristics and analyze its potential for usage as a cooling agent in thermal systems, with a focus on encouraging the use of this biodegradable green coolant. A single pipe forced convection system was used for the experimental experiments, which were focused on a temperature range of 30 °C to 100 °C and nanoparticle volume concentrations of 0.1% to 0.9%. The investigation looks at the density, heat conductivity, and viscosity of the nanofluid, among other important thermo-physical characteristics. The findings show that the coolant's density exhibits an inverse relationship with temperature, increasing as nanoparticle dispersion occurs. At a concentration of 0.9% and room temperature, the dynamic viscosity was 0.0096 kg m−1.sec. A 0.9% concentration of nanoparticle dispersion resulted in a significant increase in thermal conductivity of 27.8%. The effectiveness of the nanofluid is demonstrated by the measurement of pressure drop and convective heat transfer coefficients across the flow channel. The maximum convective heat transfer coefficient of 262.2 W m−2K−1 was recorded at a discharge rate of 17.5LPM and a concentration of 0.9% of nanoparticles. A temperature of 70 °C was found to yield the best heat transfer coefficient and the least amount of pressure loss when the nanoparticle volume percentage was 0.65%.

Melting performance of Molten Salt with nanoparticles in a novel triple tube with leaf-shaped fins

Energy demand has greatly increased today and phase change storage technology is rapidly growing due to its renewable nature. This study explores a new Triple Tube Heat Exchanger (TTHX) model, which divides phase change materials (PCMs) into two regions to improve the connection between TTHX and PCM, to improve the thermal conductivity of PCMs with different fins' number, arrangement, and angle, consequently enhancing thermal storage efficiency. A more efficient exchanger is developed by using Molten Salt as PCM and adding TiO2 and Al2O3 nanoparticles with different concentrations. Liquid fraction, temperature, and velocity obtained from numerical simulation are employed to characterize thermal storage efficiency. ANSYS 2022R1 is used for pre-modeling and numerical computations. The simulation results are turned into graphs and charts for PowerPoint and Origin analysis. We find that PCM's heat transfer efficiency is increased by 34.3 % when effective fins are added, and the addition of 5%TiO2 further increases it by 8.73 %. With the addition of Al2O3 and its concentration variation, combined with the effective fins, the heat transfer efficiency of the PCM can be enhanced by 40.73 %.

Integrating smart manufacturing techniques into undergraduate education: A case study with heat exchanger

The process systems domain is undergoing the fourth industrial revolution, which is helping industries digitize and optimize their production techniques. Concurrently, the field of data-based modeling has been expanding, leading to the proposal of many fault detection models. However, the rapid expansion has created gaps in the field. For instance, Smart Manufacturing (SM) methodologies have yet to be incorporated into undergraduate chemical engineering education. Additionally, only a few developed fault detection models have been deployed for real-time usage and practical applications. This study takes a crucial step toward bridging the two mentioned gaps by enabling undergraduate students to learn SM techniques and developing a safe and controlled academic environment for deploying fault detection models. The demonstration is implemented on a shell and tube heat exchanger, taught in a senior year laboratory course, using the Smart Manufacturing Innovation Platform (SMIP). The implementation provides an easily customizable pipeline for SM applications involving human-in-the-loop decision-making on a real-life hardware system. Actual data from heat exchanger equipment is used to train and compare the performances of several state-of-the-art fault detection models, including fully connected, convolutional, and recurrent neural networks. Current work also presents tutorials on deploying models for practical real-time applications using the SMIP. The overall architecture is a plug-and-play package that will motivate students to learn about SM and catalyze their interest in developing and deploying fault detection models using real-world data.

Design of metal foam baffle to enhance the thermal-hydraulic performance of shell and tube heat exchanger

Solid baffles are widely used in shell and tube heat exchanger (STHX), while the highly increased flow resistance and dead zones remain serious drawbacks in the applications. To address this issue, metal foam baffle is proposed in this study to replace solid baffle. The numerical model with considering the thermal non-equilibrium between fluid and foam baffles was established. Laminar flow is assumed in the foam baffles region and the realizable k-ε turbulence model is assumed in the open region. Effects of porosity, pore density, thickness and number of foam baffle (N) on the performance were examined. Results show the foam baffles always lead to lower pressure drop of STHX compared to the solid baffles. Compared to five 2 mm thick solid baffles, five 6 mm thick metal baffles with the porosity of 0.80, 0.85 and 0.90 results higher outlet temperature at the pore density greater than 80, 120 and 160 PPI, respectively. The metal foam baffle leads to higher outlet water temperature compared with solid baffles at the baffle number N ≤ 7. The foam baffles with optimum pore parameters reduced the pressure drop by 12.9 % and increase the outlet and inlet temperature difference by 31.0 % compared to the solid baffles.

Heat transfer enhancement and pressure drop performance of Al2O3 nanofluid in a laminar flow tube with deep dimples under constant heat flux: An experimental approach

This study examines the heat transfer enhancement and pressure drop of Al2O3 nanofluid in deep dimpled tubes in both longitudinal and circumferential directions. It explores mechanisms that improve the thermal performance of this novel tube geometry. Experiments were conducted using plain and deep dimpled tubes under laminar flow with Reynolds numbers from 500 to 2250, a constant heat flux of 10,000 W/m2, and nanofluid concentrations from 0.1 wt% to 1 wt%. The findings indicate that local velocity enhancement, vortex generation, and flow rotation and mixing are the three main mechanisms that improve the thermal performance of deep dimpled tubes. The results demonstrate that a deep dimpled tube with 1 wt% nanofluid can increase the convective heat transfer coefficient by up to 3.42 times compared to a smooth tube at Re = 2250. At this Reynolds number, the Nusselt number reaches a maximum of 41.80, and the friction factor ratio increases by only 1.82. Additionally, circumferential analysis reveals how dimple-induced vortices enhance heat transfer. The results also indicate that the tube geometry modification changes the flow regime zones, allowing turbulent flow at lower Reynolds numbers near Re = 2000, as identified by Nusselt number and friction factor plots. The deep dimpled tube has a low improvement penalty, with the highest friction factor of 0.38 at Re = 500 and high thermal enhancement, resulting in a performance evaluation criterion (PEC) of up to 2.80 in the studied region. However, the deep dimpled tube is unsuitable for Reynolds numbers below 1000. For higher velocities, replacing simple tubes with deep dimpled tubes in traditional heat exchangers is highly recommended.

Numerical analysis on the flow and heat transfer characteristics of heat exchanger with cruciform tube

The heat exchanger (HE) is widely used in energy and power industries, which has a vital impact on the stability and efficient operation of relevant industrial systems. Different shaped heat exchange tubes are often designed specially to improve the thermal–hydraulic efficiency of HEs. In the study, two new geometries named the cruciform twisted tube and cruciform straight tube are introduced, and the heat & mass transfer properties of liquid lead (Pb) and supercritical carbon dioxide (s-CO2) in the HEs are numerically studied to assess the thermal–hydraulic efficiency and application prospect of two kinds of cruciform tube HEs. The results demonstrate that the unique cross-section geometry of the cruciform tube improves the uniformity of the flow field, and the spiral structure of the cruciform twisted tube effectively improves the blending and turbulence of working fluid. The cruciform tube can improve the comprehensive performance of the HE by more than 12%.

Experimental study on flow and heat transfer of High-Pressure helium flow in compact helical tube heat exchanger in HTGR

In this study, experiments were conducted on helium flow within a compact helical tube heat exchanger. High-temperature helium and deionized cooling water, flowing in opposite directions, were allocated to the shell side and tube side, respectively. The Reynolds number of helium ranged from 3 × 103 to 1.6 × 104 under an operational pressure of 2.1 MPa. Measurements were taken for helium temperature, tube outer-surface temperature distribution, pressure, and mass flow rate to illustrate the flow and heat transfer characteristics. Sensitivity analysis of thermal–hydraulic parameters, including heat transfer power and efficiency under various operational conditions, was performed. The convective heat transfer coefficient and pressure drop were calculated. The transition point (Re = 9000) between laminar and turbulent flow of helium on the shell side was identified, and empirical correlations for the Nusselt number and friction coefficient were proposed. The experimental results indicate that the heat transfer performance of helium in the compact helical tube heat exchanger exceeds that of water in large-scale helical tube heat exchanger by approximately 20.75 % under fully developed turbulence, while the flow resistance characteristics remain essentially consistent.

Thermo-hydraulic performance of parallel multi-shell and multi-helical coiled tube heat exchanger CFD model with Taguchi-grey relational analysis

This study utilized four distinct shell and helical tube heat exchanger layouts to numerically evaluate the thermal and hydraulic efficiency of each arrangement. The numerical research was conducted using ANSYS FLUENT 2022R1. Currently, there has been no research conducted on the investigation of multiple helical coiled tubes enclosed by multiple shell heat exchangers. This study aimed to optimize various tasks using the Grey Relational Analysis approach in combination with the Taguchi method to maximize thermal efficiency and minimize pressure drop.A parallel configuration was used to connect two to three concentric helical tubes, with each helical tube being enclosed by a shell to control the flow of fluid. The P–P-2M − 36 design, consisting of two helical tubes, has the highest enhancement ratio of Uo = 26.75 %, when compared to the P–P-3M − 36 configuration. Similarly, the P–P-2M − 42 configuration enhances Uo by 38.42 % in comparison to the P–P-3M − 42 configuration. These findings demonstrate that a configuration consisting of two helical tubes exhibits a higher enhancement ratio of Uo compared to a configuration consisting of three helical tubes. The P–P-3M − 36 design, which consists of three helical tubes, exhibits a minimum pressure drop of 39.19 % compared to the P–P-2M − 36 configuration. Similarly, the P–P-3M − 42 configuration reduces pressure drop by 37.76 % compared to the P–P-2M − 42 configuration. The P–P-3M − 36 configuration is designed to simultaneously reduce pressure drop and boost heat transfer rate. The model achieves the optimal values for heat transfer rate and pressure drop at a Reynolds number of 55,000.